I started another thread here to try to stir up some discussion about it: What methods do you use when studying languages?
See also Language Learning and Mnemotechnics in Second Language Learning.
Have you tried experimenting with a memory town? I’m not sure how Mandarin is organized.
I haven’t tried to learn any languages in a long time, but I was recently editing the Hebrew words on Memory League and ended up signing up for a Hebrew class. (My level is very basic.) I use mnemonic images for words, trying to place them in locations, but I don’t put them in a memory palace. I use the method of loci for some of the grammar. I’m going to add a memory town once I understand the logic of the verbs better.